On 3/17/23 15:33, Andrii Nakryiko wrote:
On Wed, Mar 15, 2023 at 7:37 PM Kui-Feng Lee <kuifeng@xxxxxxxx> wrote:Introduce bpf_link__update_map(), which allows to atomically update underlying struct_ops implementation for given struct_ops BPF link Signed-off-by: Kui-Feng Lee <kuifeng@xxxxxxxx> --- tools/lib/bpf/libbpf.c | 30 ++++++++++++++++++++++++++++++ tools/lib/bpf/libbpf.h | 1 + tools/lib/bpf/libbpf.map | 1 + 3 files changed, 32 insertions(+) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 6dbae7ffab48..63ec1f8fe8a0 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -11659,6 +11659,36 @@ struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map) return &link->link; } +/* + * Swap the back struct_ops of a link with a new struct_ops map. + */ +int bpf_link__update_map(struct bpf_link *link, const struct bpf_map *map) +{ + struct bpf_link_struct_ops *st_ops_link; + __u32 zero = 0; + int err, fd; + + if (!bpf_map__is_struct_ops(map) || map->fd < 0) + return -EINVAL; + + st_ops_link = container_of(link, struct bpf_link_struct_ops, link); + /* Ensure the type of a link is correct */ + if (st_ops_link->map_fd < 0) + return -EINVAL; + + err = bpf_map_update_elem(map->fd, &zero, map->st_ops->kern_vdata, 0); + if (err && err != -EBUSY)Why is it ok to ignore -EBUSY? Let's leave a comment as well, as this is not clear.
got it!
+ return err; + + fd = bpf_link_update(link->fd, map->fd, NULL); + if (fd < 0) + return fd; + + st_ops_link->map_fd = map->fd; + + return 0; +} + typedef enum bpf_perf_event_ret (*bpf_perf_event_print_t)(struct perf_event_header *hdr, void *private_data); diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index db4992a036f8..1615e55e2e79 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -719,6 +719,7 @@ bpf_program__attach_freplace(const struct bpf_program *prog, struct bpf_map; LIBBPF_API struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map); +LIBBPF_API int bpf_link__update_map(struct bpf_link *link, const struct bpf_map *map); struct bpf_iter_attach_opts { size_t sz; /* size of this struct for forward/backward compatibility */ diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index 50dde1f6521e..cc05be376257 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -387,6 +387,7 @@ LIBBPF_1.2.0 { global: bpf_btf_get_info_by_fd; bpf_link_get_info_by_fd; + bpf_link__update_map;nit: this should go before bpf_link_get_info_by_fd ('_' orders before 'g')
ok!
bpf_map_get_info_by_fd; bpf_prog_get_info_by_fd; } LIBBPF_1.1.0; -- 2.34.1
